Sylpheed/tools/re-capture/waitobj_report.py

#!/usr/bin/env python3
"""Turn the gdb wait-object dumps into a table, discarding what does not check out.

The two waiting functions do not put the same thing in %rbx (see
freeze_waitobj.sh), so they are parsed separately:

    Wait          rbx = this           -> [rbx]        is the vtable
    WaitMultiple  rbx = XObject**      -> [[rbx+8i]]   is object i's vtable

%ebp holds the count only at the prologue: WaitMultiple reuses it at 8fc158
(`mov 0x10(%rax),%ebp`), and it reads 0 at the point these captures interrupt.
So the array length is NOT taken from a register -- entries are read until one
stops resolving, which is the same self-validating rule used for everything
else here.

Every reading is validated the same way: gdb's `info symbol` must resolve it to
a `vtable for ...` symbol. A polymorphic object's first word always is one, so
anything else is a misread and is COUNTED but not interpreted. That check is
what the reading is worth -- without it a stale register looks like a result.
"""
import re, sys, collections

VT = re.compile(r'vtable for ([\w:]+) \+ (\d+)')
HDR = re.compile(r'=== (\w+) T(\d+) (Wait|WaitMultiple) f(\d+) ===')

def parse(tag):
    """-> list of (thread, kind, count, [vtable-or-None per slot])"""
    try:
        txt = open('/tmp/fz-obj-%s.txt' % tag, errors='replace').read()
    except FileNotFoundError:
        return []
    out, cur = [], None
    for line in txt.splitlines():
        line = line.replace('(gdb) ', '')
        h = HDR.search(line)
        if h:
            if cur: out.append(cur)
            cur = dict(th=h.group(2), kind=h.group(3), count=None, slots=[], bad=0)
            continue
        if not cur: continue
        m = re.search(r'rbp\s+0x[0-9a-f]+\s+(\d+)', line)
        if m: cur['count'] = int(m.group(1)) & 0xffffffff
        if 'info symbol' in line or line.startswith('$'): continue
        v = VT.search(line)
        if v:
            cur['slots'].append(v.group(1))
        elif 'No symbol matches' in line:
            cur['slots'].append(None); cur['bad'] += 1
    if cur: out.append(cur)
    return out

def report(tag):
    recs = parse(tag)
    print('=== %s: %d wait frames ===' % (tag, len(recs)))
    if not recs: return collections.Counter()
    tally = collections.Counter()
    for r in recs:
        # take entries up to the first one that did not resolve
        live = []
        for s_ in r['slots']:
            if s_ is None: break
            live.append(s_)
        for s in live:
            tally[s if s else '<unresolved>'] += 1
        print('  T%-4s %-13s n=%d  %s' % (
            r['th'], r['kind'], len(live),
            ', '.join(live) or '(nothing readable)'))
    print('  --- objects waited on:')
    for k, c in tally.most_common():
        print('      %-45s %d' % (k, c))
    return tally

def per_thread(tag):
    d = {}
    for r in parse(tag):
        live = []
        for s_ in r['slots']:
            if s_ is None: break
            live.append(s_.replace('xe::kernel::', ''))
        d[int(r['th'])] = '%s(%s)' % (r['kind'], ','.join(live))
    return d


def diff_threads(a, b):
    """The tally alone hides the signature -- WHICH thread moved is the result."""
    x, y = per_thread(a), per_thread(b)
    print('=== per-thread %s -> %s ===' % (a, b))
    print('  %-6s %-32s %-32s' % ('thread', a, b))
    for t in sorted(set(x) | set(y), reverse=True):
        fa, fb = x.get(t, '--'), y.get(t, '--')
        print('  T%-5d %-32s %-32s %s' % (t, fa, fb, '' if fa == fb else '  <-- CHANGED'))


def stability(tags):
    """Which thread states hold STILL across repeated samples of one healthy run?

    Written after a frozen-vs-healthy diff was read as a signature and did not
    reproduce: the healthy state varies between instants too, so a difference of
    two samples is not yet a difference of two states. Anything that moves here
    is disqualified as freeze evidence before it is ever used as such.
    """
    snaps = [(t, per_thread(t)) for t in tags]
    snaps = [(t, d) for t, d in snaps if d]
    if len(snaps) < 2:
        print('need at least 2 usable captures, got %d' % len(snaps)); return
    threads = sorted({t for _, d in snaps for t in d}, reverse=True)
    print('=== stability across %d healthy captures: %s ===' % (
        len(snaps), ', '.join(t for t, _ in snaps)))
    stable = moved = 0
    for th in threads:
        vals = [d.get(th, '--') for _, d in snaps]
        uniq = sorted(set(vals))
        if len(uniq) == 1:
            stable += 1
            print('  T%-5d STABLE   %s' % (th, uniq[0]))
        else:
            moved += 1
            print('  T%-5d VARIES   %s' % (th, '  |  '.join(vals)))
    print('  --- %d stable, %d vary across healthy play' % (stable, moved))
    print('  Only a thread in the STABLE set can carry a frozen-state signature;')
    print('  a VARIES thread differing when frozen proves nothing.')


if __name__ == '__main__':
    if sys.argv[1:2] == ['--stability']:
        stability(sys.argv[2:]); sys.exit(0)
    tallies = {t: report(t) for t in (sys.argv[1:] or ['healthy'])}
    if len(tallies) > 1:
        a, b = list(tallies)
        print('=== %s -> %s ===' % (a, b))
        keys = set(tallies[a]) | set(tallies[b])
        for k in sorted(keys):
            x, y = tallies[a][k], tallies[b][k]
            print('   %-45s %3d -> %-3d %s' % (k, x, y, '' if x == y else '  CHANGED'))
        diff_threads(a, b)